Chapter 3 (3-3.4) Flashcards
Explain what a sample is.
“A sample is a subset of observations from a target population. A representative sample accurately reflects the characteristics of the population from which it is drawn.”.
What does “n” refer to?
The number of observations in a sample.
What does “N” refer to?
The number of observations in a target population.
What does “sd(X)” stand for?
It stands for “the standard deviation of X”.
Knowing the standard deviation of a variable helps you what?
It helps you understand the range of the data.
What does a histogram show?
The distribution, mean, and spread of a variable.
The subset of individuals chosen for a study is called what?
A “sample”.
What’s the best way to make a representative sample of a group of individuals (e.g. CBS students)?
By using random sampling.
True or false: by using random sampling, the treatment is assigned at random.
True
True or false: by using random treatment assignment, individuals are selected at random.
True
True or false: both random sampling and random treatment assignment use a random process and refer to the same concept.
False
How can you better understand the content and distribution of each variable in a dataset?
By creating a frequency table, a table of proportions, a histogram, and computing descriptive statistics.
What are the two measures of centrality?
- mean
- median
What are the two measures of spread?
- standard deviation
- variance
True or false: when a dataset contains an even number of observations, the median is the highest of the two middle numbers.
False (the median is the average of the two middle numbers)
True or false: the larger the standard deviation, the flatter the distribution.
True
How do you calculate the variance of a variable?
The square of the standard deviation.
